Computer and processing circuits use a clocking signal to synchronize the operation of internal circuits. The clocking signals are always present whether or not the processing circuits are actually processing data or awaiting further inputs. During these waiting periods, the normal operation of the processing circuit results in a waste of power. This is especially disadvantageous to a processing circuit having a fixed power source such as a battery.
Battery powered processing circuits are common in portable calculators. One technique for conserving battery power is contained in U.S. Pat. No. 4,317,181 entitled "Four Mode Microcomputer Power Save Operation" that discloses the means to turn off clocked logic while power is maintained to certain specific circuits connected to the memory. In a related patent, U.S. Pat. No. 4,409,665, a processor circuit is disclosed that includes logic forced to a predefined output logic level during inactivity. Power consumption is less when the logic is at this predetermined output logic level.
A similar type technique is disclosed in U.S. Pat. No. 4,317,180.
U.S. Pat. No. 4,218,876 entitled "Combined Timekeeper and Calculator with Low Power Consumption Features" discloses a dual mode calculator wherein the clocking signals are modified to create additional signals when the calculator is in one specific mode.
A further technique is disclosed in U.S. Pat. No. 4,203,153 entitled "Circuit for Reducing Power Consumption in Battery Operated Microprocessor Base Systems" that includes a circuit for disconnecting the microprocessor from a battery source for a predetermined time interval.